Papillomatous Digital Dermatitis (PDD) is a chronic infectious and apparently contagious disease of the feet and/or lower legs of cattle. The disease is known by several common and scientific names including digital dermatitis, interdigital papillomatosis, digital papillomatosis, verrucous dermatitis, footwarts, hairy footwarts, hairy heelwarts, raspberry heel, strawberry foot disease and strawberry footrot. It has been identified as one of the most significant diseases facing the dairy industry today. The disease results in lameness which leads to economically significant reductions in milk production and concomitant declines in animal health such as body weight loss, and fertility. It is believed that the agent can be brought onto a dairy via introduction of new stock or formite transmission from hoof trimmers, dairy testers, muddy boots on veterinarians, etc. In dairies currently experiencing losses from the disease, it has been estimated that the cost in lost milk production, reproductive losses and increased culling averages at least $100 per day.
To date, only two control methods have shown promise: use of antibiotics topically (cleaning, curettage and bandaging each foot) or parenterally (problematic for reasons of milk withdrawal), and the use of bacteriocidal footbaths (antibiotics, formaldehyde, iodine, etc.). Although many lesions may respond well to antibiotics or footbaths containing antibacterial compounds, recurrences are known to occur and some evidence suggests development of antibiotic resistance. These approaches are labor intensive, prone to human error, costly (antibiotics for 30 days of footbaths runs $2,500 for a 400 cow dairy), subject to governmental restrictions, and do not confer either environmental cleanup or lasting protection from recurrence.
In view of the significant economic damage caused by PDD, an effective way to detect and treat animals infected with the disease, as well as a means to protect them against future infection, is highly desirable.